The present invention relates generally to clarifiers and like devices for separating and removing solids from a liquid suspension, and more particularly to an improvement in a clarifier which will allow the clarifier to continue its normal operation while maintenance or repairs are carried out.
It is customary to subject sewage and other waste waters containing suspended solids to sedimentation using a process called clarification, wherein the solids settle out, and are removed. A variety of equipment is available for such an operation. However, repairs and maintenance to such equipment is difficult to carry out without shutting down the operation of the clarifier. This is a high risk approach since many clarifiers presently in use are operating at or near their design capacity.
Clarification using a typical center column clarifier is conducted by introducing the liquid suspension to be clarified into a circular tank from below through an incoming effluent pipe and up a center column. The effluent exits the center column at a point below the nominal level of the pool of liquid in the clarifier tank. The liquid suspension in the tank is gently agitated so that the solids are settled out. The clarified liquid is removed at an overflow generally referred to as a launder, located near the periphery of the top of the tank, and the settled solids are raked from the bottom of the tank, where they are collected in a sludge pit for removal. The flow of the liquid suspension up through the center column and out into the tank is forced by a hydraulic head from the source or by pumping. In operation, the clarified liquid removed from the tank is either further treated, or is discharged into a suitable pond, river or the like. Meanwhile, the solid material is collected by the rakes at the bottom of the tank and is pumped offsite where it can be stored or disposed of as for example, by recycling, burning or other means. Because the clarification process is essentially a continuous process, it may be seen that shutting down the clarifier for maintenance or repairs is risky and can cause interruptions in service or back-ups that are undesirable.
Examples of typical clarifier installations are shown for example in the following U.S. Pat. Nos. 2,568,452; 2,713,026; 3,175,692; and 3,486,628. However, none of these patents address the need for providing for the continued operation of the clarifier during maintenance or repair.